Screen



July 13 1926. 1,591,959

J. BLAND SCREEN Filed May 17. 1924 njzand 27 Q?" q- G2,,

Jittori'zciypi screen does not do so.

' ticles.

-Patented July 13, 1923.

JOHN BLA ND, OF CHICAGO, ILLINOIS.

SCREEN.

Application filed May 17,

This invention relates to screens, and has for one object to providemeans and a process whereby the operation of screens is rendered moreetlicient and rapid and whereby the percentage of material of the propersize which fails to go through the screen is greatly reduced.

I have found that in the case of vibratory screens and particularly withscreens which vibrate at a very rapid rate, a considerable portion ofmaterial small enough to pass through the mesh or perforations of theThis is due to many causes, one of the most important being the highrate of vibration of the screen and the vigorous and extreme motionimparted to the particles during screening. In connection with avibratory screen the particles are frequently thrown into the air adistance equal to several times their thickness. Upon coming down if theparticle is just a little smaller than the opening through the screen,unless it strikes exactly in line with the opening it will not passthrough it but will bounce and be driven off again. This process will berepeated until the particle which should have passed through the screenpasses off at the end.

Another object of my invention is therefore to provide a process andmeans for damping the degree of movement of the par- Another object isto provide means whereby the particles are held comparatively close tothe screening surface, and thus caused to vgo somewhat more readilythrough'the screen. Other objects will appear from time to timethroughout the specification and claims.

7 My invention is illustrated diagrammatically in the drawings, wherein:

Figure 1 is an elevation showing my device applied to a vibratoryscreen;

Figure 2 is a view similar to Figure 1 showing my device applied to ashaking screen;

Figure 8 is a view more or less accompanying similar to the precedingviews showing a modification of my device.

Like parts are designated by like characters throughout.

device in connection with a vibratory and a shaking screen, and it isapplicable to both. It is applicable also to practically any other typeof screen, although it is probable that it has its greatest I have shownmy 1924. Serial No. 713,899.

importance in connection with vibratory screens, because generally insuch screens the rapidity of motion is such as to cause the particles ofmaterial onthe screen to be out of contact withthe screen throughout aconsiderable portion of the time within which screening should takeplace. It is therefore with screens of this type that it is ofparticular importance to prevent excessive movement of particles awayfrom the screen.

As illustrated in Figure 1 my invention comprises a screen frame Ahaving a screen A fixed in it. As here shown the screen is of metalliccloth but any type of screen might, of course, be used. The screen ispivotally mounted upon a support B, at one end and is carried upon asecond support C at its other end. The support G is held at each endagainst lateral movement and is formed of spring material. One or moresuch supports may be used. As here shown two such spring supports Cwould be used but any number might be so used. Mounted upon each of thespring supports 0 is a hearing C within which is mounted for rotation ashaft C This shaft has preferably fixed upon it a pulley G which isdriven through a belt G mounted upon a motor C V Mounted upon the shaftG is a fly wheel D. This pulley may be of any suitable form and as shownhere is provided with spokes, one of which has mounted upon it anadjustable weight D This weight is provided so that the pulley isslightly out of balance. The degree of this condition may be varied bythe variation in the position of the weight D Then the shaft is driventhe members 0 are caused to vibrate laterally by reason of the unbalanceof the fly wheel D. This lateral vibration sets up a vertical movementat the end of the support and thus a vertical component of vibration issupplied and the screen itself is vibrated.

Mounted on'the screen is a bar or other suitable member -E. Fastened tothis memher and trailing loosely from it is a fabric piece E This piecelies on top of the screen and is in contact with the screen fabric orthe screening member used. The material to be screened is deposited onthe screen fabric at its upper end through a chute F.

As shown in Figure 2 the screen A is mounted for shaking or lateralreciprocation. port G and at the other upon a somewhat longer support Gand has connected to it a rod G which is connected to any suitablesource of motion whereby the screen is caused to shake or oscillate. Thescreen has mounted on it a member E like that shown in Figure 1. Fromthis member depends a fabric E which is like that shown in Figure 1.This fabric may be loose at its other end or it may be fastened to a rodE This is not essential, but when the fabric is used in connect-ion withan oscillating screen it is sometimes an advantage, as it overcomes anytendency of the cloth to form into folds which might otherwise occur dueto the longitudinal movement of the screen.

As shown in Figure 3 a somewhat different type of screen appears. Thescreen is carried in a frame H which is mounted for movement on supportsH H As here shown the screen is adapted to be shaken in the same manneras is the screen shown in Figure 2. It might also of course be avibratory screen such as the one shown in Figure 1. The screen cloth Iis similar to that shown in the preceding figures although a differentconstruction might be used. In this form'of the screen instead of thefabric shown in Figures 1 and 2 a screen fabric J is used. This isperforated and is preferably provided with perforations somewhat largerthan those of the main screening cloth fixed in the frame. his secondthickness of screening cloth is mounted for slight movement but is heldagainst excessive movement by means of the flexible connection JAlthough I have shown an operative device, still it will be obvious thatmany changes might be made in size, shape and arrangement of partswithout departing materially from the spirit ofmy invention; and I wish,therefore, that my showing be taken as in a sense diagrammatic.

The use and operation of my invention are as follows:

As shown in Figures 1 and 2 the fabric which lies over the screeningsurface proper rests freely upon the screen. Material to be screenedpasses between it and the screen cloth. 'hen due to the action of thescreen material thrown upward from the surface of the screen, it strikesthe loosely lying piece of cloth and its movement is greatly limited. Byreason of this it has been found that material passes very much morereadily through the screen and that a very much smaller percentage ofmaterial of a size which should pass through the screen, fails to do so.

The form shown in Figure 2 is practically identical ,with that shown inFigure 1. The operation of the screen is somewhat dif It is carried atone end upon a sup ferent, since its shaking is lateral rather thanvertical, but in this case also the maerial on the screen as it is movedfrom the screen surface proper and thrown upward, comes in contact withthe fabric above it and its upward movement is limited, if not entirelyprevented and movement of the material through the screen is greatlyaccelerated. By the use of this construction the size of the screen maybe materially reduced because the material moves through the screen verymuch more readily than is the case without the fabric covering.

In the form shown in Figure 3, in place of the fabric covering a secondscreen is used. This screen is loose with relation to the main screenand is mounted for movement with relation to it. The material to bescreened is deposited on top of it and must pass through to reach thescreening surface proper. Once this is done, the action which is carriedout in connection with the screening fabric described above is to someextent repeated, that is to say, ma-

terial on the lower screen surface as it driven or thrown up to someextent contacts the upper loose screen and its upward movement is thuslimited or prevented and passage of the material through the lowerscreen is accelerated. There is, however, in connection with this formanother action not present in the forms shown in Figures 1 and 2. lVherevery fine material is to be screened it is frequently found that as itmoves along the screen it tends to form into balls which are too largeto pass through the mesh of the screen and thus move off at the end.\Vhen the double screen is used, the relative movement of the upper andlower screen and the movement of the material which is being screenedbetween the two and from one to the other tends to preventthe formationof these balls and to break them up when formed. Thus the screen shownin Figure 3 in addition to limiting excessive movement away from thescreen of the material which is being screened, serves also to preventthe formation of balls of material and break up such balls when onceformed.

I claim: I

1.. In combination with a high speed vibratory screen, including ascreening surface adapted to be moved to cause screening action, abafiling element substantially impermeable by the material to bescreened, loosely associated with the screening surface and resting uponit to limit the movement of material being screened away from the screenduring the screening action.

2. In combination with a high speed vibratory screen, including ascreening surface adapted to be moved to cause screening action, aflexible battling element substantially impermeable by the material tobe screened and resting upon the screen to limit the movement ofmaterial being screened away from the screen during the screeningaction.

3. In combination with a high speed vibratory screen,'including ascreening surface adapted to bemoved to cause screening action, aflexible baffling element substantially impermeable by the material tobe screened loosely associated with the screening surface and restingupon it to limit the movement of material being screened away from thescreen during the screening action.

4. In combination with a high speed vibratory screen, including ascreening surface adapted to be moved to cause screening action, aflexible baffling element substantially impermeable by the material tobe screened to limit the movement of material being screened away fromthe screen and resting upon it during the screening action, saidbaffling element supported at one end above the screen and restingelsewhere freely upon the screen.

5. In a high speed vibratory screening device a fran'ie in which ismounted screening means, a supporting element of spring material for oneend of said frame, means supporting the other end of said frame topermit movement, and means for vibrating said spring member wherebygenerally Vertical reciprocation of the screening means is effected, incombination with a bafliing element substantially impermeable by thematerial to be screened to limit the movement of material being screenedaway from the screen during the screening operation said bafflingelement resting upon the screening surface.

6. In a high speed vibratory screening device a frame in which ismounted screening means, a supporting element of spring material for oneend of said frame, means supporting the other end of said frame topermit movement, and means for vibrating said spring member at a highspeed with a hori-' zontal amplitude whereby vertical reciprocation ofthe screen means is effected, in combination with a baffling elementsubstantially impermeable by the material to be screened to limit themovement of material being screened away from the screen during thescreening operation.

7. In a high speed vibratory screening device a frame in which ismounted screening means, a supporting element of spring ma terial forone end of said frame, means supporting the other end of said frame topermit movement, and means for vibrating said spring member at a highspeed with a horizontal amplitude whereby vertical reciprocation of thescreen means is effected, in combination with a baflling element substantially impermeable by the material to be screened to limit themovement of material being screened away from the screen during thescreening operation, said element being located above the screen andresting upon the screen surface.

8. In a high speed vibratory screening device, a frame in which ismounted screening means, a supporting element of spring material for oneend of said frame, means supporting the other end of said frame topermit movement, and means for vibrating said spring member at a highspeed whereby generally vertical reciprocation of the screening means iseffected, in combination with a baffling element substantiallyimpermeable by the material to be screened to limit the movement ofmaterial being screened away from the screen during the screeningoperation, said element being located above the screen and restingloosely upon it.

9. In a high speed vibratory screening apparatus, a screen supported ina frame, a member flexible throughout its central part and fixed at oneend against lateral movement, and contacting with the screen at theother, a rotating element out of balance and supported upon saidflexible member and adapted to vibrate said member at a high speed, incombination with a baflling element substantially impermeable by thematerial to be screened to limit the movement of material being screenedaway from the screen during the screening action.

10. In a high speed vibratory screening apparatus, a screen supported ina frame, a member flexible throughout its central part and fixed at oneend against lateral movement, and contacting with the screen at theother, a rotating element out of balance and supported upon saidflexible member and adapted to vibrate said member at a high speed, incombination with a baffling element substantially impermeable by thematerial to be screened tolimit the movement of material being screenedaway from the screen during the screening action, said baffling ele mentbeing above the screen.

11. In a high speed vibratory screening apparatus, a screen supported ina frame, a member flexible throughout its central part and fixed at oneend against lateral move ment, and contacting with the screen at theother, a rotating element out of balance and supported upon saidflexible member and adapted to vibrate said member at a high speed, incombination with a baffling element substantially impermeable by thematerial to be screened to limit the movement of material being screenedaway from the screen during the screening notion, said baflling elementbeing above the screen and loosely supported upon the screen throughouta portion of its length.

12. In combination with a high speed vibration screen including a frameand a perforated screening surface adapted to be moved at high speed tocause screening ieo action, a flexible balliing element substantiallyimpermeable by the material to be screened adapted to be superimposedupon said screening material above the material to be screened tolimitthe movement of said material away from the screen during thescreening action, said bafiiing element supported at one end in thescreen frame above the screening surface and elsewhere resting freelyupon the screening surface.

Signed at Chicago, county of Cook and State of Illinois, this 14th dayof May, 192-11 JOHN BLAND.

